1. Field of the Invention
The present invention relates to industrial process field instrumentation, and more particularly to industrial process field instruments employing reference signals transmitted from satellites.
2. Discussion of the Related Art
It is a common problem in the controls industry to be able to interrogate and gather information from remotely located field installations which may be separated by many miles from a master or control location. In such instances, there is a common need to know precise information, such as flow rate information, pressure information, quantitative information relating to storage, etc. Most present day systems employ hard wire solutions to provide information from remote field locations to a master or control point. Telephone lines, microwave and links, and in some instances fiber optic cables have been employed for this particular purpose.
A space-based satellite system commonly referred to as the Global Positioning System (GPS) is presently in operation for transmitting to ground station receivers accurate positional and time synchronization signals. The GPS signals transmitted are detected and processed by a GPS receiver and used to derive highly accurate position, altitude, speed and direction information for use by a user. For example, aircraft and ships use GPS equipment to provide en route navigation and for airport or harbor approaches. GPS tracking systems have been used to route and monitor delivery vans and emergency vehicles. The agricultural community has utilized the system to monitor and control the application of agricultural fertilizer, pesticides and the harvesting of crops. Handheld GPS receivers are currently available for use as an accurate positional aid for hikers and hunters. Since the GPS user does not need to communicate with the satellite, it can have an unlimited number of users.
Because of the highly accurate nature of the reference signals transmitted by the GPS satellites and the need of not requiring direct communication with the GPS satellites, the integration of such technology in connection with industrial process field instrumentation exhibits advantages for providing location, time-stamped and time-synchronized information between two or more industrial process field transmitters and/or a master controller or other intermediate control points within an industrial control system.
Accordingly, it is the object of the present invention to utilize the GPS system in connection with an industrial control system whereby the location of various field instrumentation can be accurately located, as well as the conditions of such field instruments can be determined, detected and transmitted back to a master or control location and used by instrument technicians to locate instruments that may require servicing.
It is another object of the present invention to utilize GPS reference signals and derived GPS time signals from a GPS receiver with industrial process field instrumentation to provide time-stamp and time-synchronized data for measurement and diagnostic applications within an industrial control system.